A lot more depends on fossil  fuels than you might expect.

Like your medicine cabinet. No, not the plastic pill bottles… the pills  themselves might be derived from crude oil.

Indeed, one of our most commonly-used drugs uses  a component of crude oil as a starting material. And that drug is: Tylenol! Which is, by the way, safe and  effective, including during pregnancy.

Hence why it’s commonly-used. More than 15,000 metric tons are  produced globally every year. Which means a lot of petroleum goes into  that needed, safe and effective pain relief.

Unless we didn’t have to use oil.. It is possible to recycle  plastic and turn it into Tylenol. Not possible for us humans, though – we  need a hand from a pretty unexpected place. [♪ INTRO] Crude oil contains the starting chemicals  needed for a bunch of things you might not   think of, from shaving cream to paintbrushes,  clothing to fertilizers… and acetaminophen.

AKA Tylenol. Also called paracetamol outside the US. We’ll just stick to calling  it Tylenol for this video,   though keep in mind we mean  the substance, not the brand..

See, Tylenol is made up of carbon,  nitrogen, oxygen and hydrogen. But the thing about chemical synthesis  is that you can’t just pick out the   elements you want and stick them  together like building bricks. There are only certain chemical  reactions that are physically possible.

To build up a molecule with an  oxygen here and a nitrogen there,   you need the right conditions  to achieve those reactions. You also need specific starting  materials to undergo those reactions. Any old compound made of C-N-O-H just won’t do.

Current production of Tylenol starts with a  compound called benzene, isolated from crude oil. You do some fancy chemistry to add some extra  chemical groups to the benzene and voila, Tylenol. Well, it requires some chemical  processing and other ingredients,   but that’s more or less how it goes.

Point is, a more environmentally-friendly  starting material would be great. And there are options! Like a benzene-esque precursor found in trees.

But how about starting with  something we don’t want? Like used plastic. But before we learn how, we have to keep  the lights on, so let’s go to a quick break.

Thanks to our Presidents of Science,  Harry Plumley, Charlie Stanley,   and TJ Steyn, for supporting this SciShow video! These patrons of the show help  us fund things like the move away   from green screens and onto hand-crafted sets, like the stuff that we use for Deep Dives. And they help us pay the  people who make those sets.

Shout out, Hiroka! Since that change, we’ve made videos on our  Rocks Box set with its dark academia aesthetic,   our main set with its dynamic shapes and colors,   and even on location in real labs where they  conduct the studies we’re talking about! And we can only level up like that with your help.

So thank you to everyone who  has the means and chooses to   support these higher quality  videos at patreon.com/SciShow. Plastic is something we have  in excess, unlike crude oil. Kinda for the same reasons, if you think about it.

A 2017 paper estimated that there are  4900 million metric tons of plastic   in the environment… and we’ve  kept adding to that since then. Many plastics are made from fossil fuels  themselves, so they contain components   that are benzene-derived, which is  to say, possible Tylenol precursors. One type of plastic, polyethylene terephthalate or   PET, is a component of water bottles and  polyester clothing, among other things.

PET doesn’t naturally degrade,  so it can persist for centuries. Basically, we have a lot of it. Good start.

But the million dollar question is, how  do we get from plastic to painkiller? Well, first, you break down the  plastic polymers into monomers. Polymers are long chains of  molecules strung together,   and monomers are those basic building blocks.

We have helpers to speed along step one. There’s already research on  microbes that can break down PET,   turning plastic polymers into monomers. Plastic polymers aren’t something  bacteria would normally encounter,   and those molecular bonds can be tough to break.

Even so, there are several microbes  with enzymes that can do the job. Once we have our PET monomers, the next,  trickier, step is to build them up into Tylenol. In a study published in June 2025, a  group of researchers found a way to   convert PET monomers into an organic molecule  called PABA, in the presence of bacteria.

PABA is an essential nutrient for  these bacteria and, helpfully for us,   an alternative starting material for Tylenol. E. coli need PABA to make folate, and  they need folate for building DNA. Bacteria usually use other starting materials  to make PABA, so in the study the researchers   engineered E. coli that were missing some  of the steps they need in that process.

So basically, these bacteria needed PABA to  survive, and couldn’t make it the normal way. PET monomers were added to the media with  bacteria, along with various catalysts. The bacteria had to rely on PET being  converted to PABA in order to survive.

And life, as it does, found a way. This was a breakthrough. Remember we mentioned that there are  constraints in synthetic chemistry?

We have to work with the chemical  reactions that are possible,   to go from starting materials to final product. It’s like solving a puzzle, where  there are rules about legal moves. And in this case, scientists didn’t know if there   was a PET-to-PABA solution  that was non-toxic to life.

That’s because in a lab, high heat  or toxic materials would be required. But purely through this process of  artificial evolution, the bacteria found   the right conditions for what the researchers  called a biocompatible Lossen rearrangement. Biocompatible means compatible with life.

And a Lossen rearrangement is a way of  forming a specific carbon-nitrogen bond,   a necessary step in converting  the original chemical to PABA. The reaction was helped along by  phosphates in the bacterial media. The researchers showed that the  process was non-toxic to E. coli,   and enhanced by their own phosphate molecules too.

Once you have PABA, a benzene derivative,  the next stage is turning that into Tylenol. Adding a couple of genes to the engineered  E. coli enabled this conversion. An enzyme from a fungus converts PABA  to a molecule called aminophenol.

And an enzyme from another bacterium  converts aminophenol to Tylenol. The overall yield from PET  monomer to Tylenol was above 90%. But, this process needs to be scaled  up a lot to actually be practical.

Baby steps. A possible long-term goal would  be getting microbes to also do the   initial step of breaking PET polymer  down to PET monomers, all in one pot. Bacteria to break down, and bacteria to build up.

Pretty impressive. Thanks little guys! This is an example of bio-upcycling:  getting microbes to break down plastics,   then using those pieces to  create new useful materials.

The authors of the study point out  that this pipeline from plastic to   painkiller couldn’t be achieved using  chemical or biological synthesis alone. By engineering bacteria, and  using controlled conditions,   there is a synergy of chemistry and biology. It’ll take some R&D to make this cost-effective,   but Tylenol isn’t the only fossil  fuel-derived drug out there.

Maybe this proof-of-concept will set the  stage for even more plastic bio-upcycling. [♪ OUTRO]